This invention relates to an improved magnetic record member for use in magnetic recording devices such as a magnetic disc and a magnetic drum and a process for manufacturing same.
A magnetic recording device basically consists of magnetic heads for recording and reproducing (referred to simply as "head" hereinafter) and magnetic record members.
In general, recording and reproducing systems for the magnetic recording device may be classified into two types. In one system, upon the initiation of operation, a head is brought into contact with the surface of a magnetic record member and then, the record member is rotated at a given speed in a manner to provide a spacing between the head and the magnetic record member surface, thereby enabling the recording and reproducing operations. According to this system, upon completion of operation, rotation of the record member is stopped in a state where the head and record member are maintained in frictional contact with each other as is the case with the starting of operation.
In another system, after a magnetic record member is rotated at a given speed beforehand, a head is suddenly urged against the record member surface to provide a spacing due to an air layer created between the head and the record member so as to perform the recording and reproducing operations. As a result, the latter system brings the head and record member into frictional contact with each other when the head is urged against the record member surface.
Such frictional contact tends to harm the head and the magnetic record member so that satisfactory recording and reproducing operations become impossible. In addition, there is a case where the head unexpectedly contacts the record member surface so that the head and record member may both be damaged. Also, even if the head and record members are not damaged, a load is increasingly imposed on a spring for supporting the head as the contacting frequency of the head and record member is increased. For this reason, the spacing between the head and the recording surface of the member is varied. Besides these, a magnetic metal thin film medium used as the record member is possibly subjected to a high temperature and high humidity environment so that the record member surfaces experiences corrosion. This affects the magnetic characteristics of the member, and as a result, deteriorates the recording and reproducing characteristics thereof. Consequently, this requires the provision of a protective film or an over-layer on the surface of the magnetic metal thin film medium serving as one magnetic memory medium of the magnetic recording device.
The following characteristics must be required for the aforesaid protective film.
(1) A protective film medium should withstand an unexpected or inadvertent contact of a head with a magnetic record member during recording and reproducing operations (resistance to head-crushing).
(2) The load imposed on a spring should be small, which is caused by a frictional force for supporting the head exerted by frictional contact of the head with the record member at a plurality of contacting cycles (lubricity).
(3) Even due to such frictional contacts at a plurality of contacting cycles, the protective film medium should be maintained in a state which is free of damage and peeling (anti-abrasion characteristic).
(4) Even at high temperature and high humidity conditions, the protective film medium should protect the magnetic metal thin film medium so as to insure desired recording and reproducing characteristics (resistance to environmental conditions).
(5) The protective film medium should not impair the magnetic characteristics of a metal substrate including the magnetic memory medium.
U.S. Pat. No. 3,466,156 teaches the use of a polymer film and a wax lubricant film as a protective film formed by coating polyamide resins and ceresin wax. However, the use of this protective film has several disadvantages. In other words, the polymer film and the wax lubricant (film) are easily flaked off by frictional contact of a head against a magnetic record member at a plurality of contacting cycles. In this manner, this protective film fails to meet the characteristics (2) and (3).
Moreover, it is known that SiO.sub.2 is coated using a spattering process on a magnetic record member as a protective film. However, the film formed by spattering SiO.sub.2 fails to meet the characteristics (1) and (2). Also, a successful attempt to meet the characteristics (1) to (5) is known in the technique for coating glass through a spattering process as a protective film. However, the use of the spattering process unavoidably brings about the difficulty in the manufacture on a mass production basis, and hence, the cost increase in the manufacture. Also, there is another disadvantage in that the size increase in the magnetic record member is accompanied with that of the target for spattering. For this reason, technical difficulty is encountered, with an unavoidable increase in the total cost of the apparatus.
It is an object of the present invention to provide a magnetic record member and a process for manufacturing the same free of the aforesaid shortcomings in the prior art magnetic record members.